1. Field of the Invention
The present invention relates generally to a fuel tank used for automotive vehicles, and more particularly to a device for supporting a fuel feed pump within a fuel tank, that is, an in-tank fuel feed pump supporting device disposed within a fuel tank.
2. Description of the Prior Art
The background of the present invention will be explained with its application to the fuel tank used with an automotive vehicle.
In general, in an automotive vehicle, a fuel feed pump is disposed out of a fuel tank. The fuel feed pump serves to feed fuel within the fuel tank to a carburetor or a fuel injection pump. In gasoline engines, fuel feed pumps of diaphragm type are mainly used, being driven mechanically, electronically or pneumatically. On the other hand, in diesel engines, fuel feed pumps of plunger type are mainly used, being driven electrically. However, in the case where the fuel feed pump is disposed out of a fuel tank, there exists a problem in that fuel vapor is liable to be produced due to heat, for instance, in an outlet pipe communicating between the fuel feed pump and the fuel tank, thus causing vapor lock. Once vapor lock occurs in the fuel feed system, since only vapor produced within the outlet pipe is mainly compressed or expanded by the fuel pump, it is impossible to feed fuel from the fuel tank to the carburetor, for instance, smoothly.
To overcome the above-mentioned problem, a fuel tank of in-tank fuel feed pump type has been proposed, for instance, in a Weekly Service Bulletin (No. 445, page 84) published by NISSAN MOTOR CO., LTD., October 1981, in which a fuel feed pump is supported within the fuel tank. In this type of fuel feed system, since fuel is directly supplied from the fuel tank to the carburetor, for instance, by the in-tank fuel feed pump, pressure in the outlet pipe of the fuel pump can readily be increased in order to prevent fuel from being vapored, thus it being possible to prevent vapor lock effectively in the fuel feed system.
In the prior-art in-tank fuel feed pump supporting device, however, there still exist several shortcomings as follows:
(1) The vibration damping elastic members are mainly deformed substantially only in compression mode in dependence upon the mounting structure thereof. Therefore, the damping coefficients of these elastic members are relatively great, thus it being impossible to effectively damp the vibration energy of the fuel feed pump.
(2) The fuel feed pump is disposed within the fuel tank in an uncovered state. Therefore, noise generated by the fuel pump is readily strengthened by the fuel tank with the tank body serving as a resonator, thus pump noise being readily transmitted to the outside of the fuel tank.
(3) The number of vibration damping elastic members are great. Therefore, various molds are necessary; the parts stock cost is high; the assembly process is rather complicated, thus resulting in a higher manufacturing cost.
The arrangement of the prior-art in-tank fuel feed pump supporting device will be described in greater detail hereinafter with reference to FIGS. 1 and 2 under DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS.